"Although" and "though" can mean both "but" and "even though". They mean the same thing, but there are two main differences:
1) "Although" is slightly more formal.
2) "Though" can be used at the end of a sentence.
3) "Although" is more commonly used to mean "even though" than "but".
E.g.
In order from most formal to most informal:
"It's raining, although it's still very hot" = "It's raining, though it's still very hot." = "It's raining. It's very hot though."
These sentences all mean "It's raining, but it's still very hot".
"Although/Though it's raining, it's still very hot" is also possible, but it means something else. Here "although" means "even though".
You can always replace "although" with "though" (to make a sentence less colloquial), but you can only replace "though" with "although" if it isn't at the end of a sentence.